1. Field of the Invention
This invention relates generally to a solution for cleaning, storing or wetting contact lenses. More specifically, it relates to an aqueous solution containing a poly(oxyethylene)-poly(oxypropylene) substituted ethylenediamine surfactant in admixture with one or more germicide, a viscosity builder, a tonicity agent and a sequestering agent.
2. Prior Art
Contact lens technology and contact lens use has been developing and expanding rapidly since the Second World War. While contact lenses were first proposed as far back as Leonardo Da Vinci and glass lenses were in use during the early part of this century, widespread development and use did not come about until the advent of polymer chemistry in the 1930's and 1940's.
It is usual to classify contact lenses as being hard, flexible, or soft hydrogel depending upon the structural characteristics of the material used to make the lens. A second, and more useful, way of classifying contact lenses would be to designate a particular polymer as having either a hydrophilic or hydrophobic surface. Such a classification system has merit because comfortable wear and visual acuity depend in good part upon the ability of the contact lens to be compatible with the tear fluid which normally exists on the eye surface, particularly the cornea of the eye. Under normal physiological conditions, the surface of the cornea is covered by a thin film of tear fluid. This film contains sebaceous material and polysaccharide conjugated albumin and globulin known as mucin. These materials are not distributed homogeneously throughout the tear layer. Rather, the mucin is concentrated next to the surface of the cornea. Over this concentrated mucin layer is an intermediate watery layer containing highly dilute mucin overlaid with a thin layer of sebaceous material. There is an excess of albumin and globulin in the tear fluid relative to the corneal tissue fluid which produces a lowered surface tension allowing the tear film to spread evenly over the epithelial surface.
To be safe and functional it is necessary that any lens placed on the eye is in some matter completely wetted by this tear layer at all times. Uniform and continuous wetting of the lens by the tear fluid is required for comfortable wear, for providing good optical performance and for preventing the accumulation on the lens of proteinaceous and sebaceous materials.
The majority of contact lenses in use today are either the poly(methylmethacrylate) (PMMA) hard lens or the soft hydrogel lenses. Other recently developed polymers useful for contact lenses include, for example, poly(methylmethacrylate)-silicone materials (PMMA-silicone) marketed as the Polycon.RTM. lens, fluoroalkyl-methylmethacrylate polymers, the cellulose acetate butyrate (CAB) family of polymers, silicone rubber polymers and silicone-polycarbonate polymers. All have been investigated as alternatives to PMMA and soft hydrogel polymers. These new polymers are all hydrophobic. The first two new polymers mentioned above are hard lenses, while the CAB material may be hard or flexible, depending upon the acetyl-butyryl ratio, and the latter two are flexible polymers. A review of current contact lens technology can be found in the Encyclopedia of Chemical Technology, Kirk-Othmer, Ed. Vol. 6, 3rd ed. (1979) John Wiley & Sons, pp. 720-742.
Attempts are being made to create a hydrophilic surface on the hard and the flexible hydrophobic contact lenses either by coating them with a hydrophilic material during manufacture or chemically altering the surface to produce a hydrophilic surface or changing a copolymer to provide a hydrophilic material such as the hydrogel lens; but no commercially acceptable materials of this type are available to date. Some means of wetting the hydrophobic surfaces of these new lenses and the old PMMA lenses before insertion onto the eye is required for comfortable and extended wear.
There are several formulations currently known and available commercially which can serve the purpose of wetting the contact lens surface before it is inserted on the eye. Generally these solutions contain a wetting agent in combination with a germicide, some viscosity builder, and salts of some type to adjust the tonicity of the solution to make it compatible with the osmoticity of the tear fluid. The best known of these wetting agents is polyvinyl alcohol, the subject of U.S. Pat. Nos. 3,183,152; 3,549,747 and 4,131,651 in which PVA is used as a wetting agent for hard contact lenses and as a component of artificial tears. Alkylated and hydroxyalkylated cellulose polymers such as hydroxy propylmethylcellulose and methylcellulose have been described as having hydrophobic lens wetting properties but these polymers are used now mainly as viscosity builders and demulcents in conjuntion with some other wetting agent such as PVA. See Remington's Pharmaceutical Sciences, Arthur Osol Ed. 16th ed. MacK Pub. Co., Easton PA, p. 719 (1980). A third material, having the trademark Pluronic, has been disclosed as a wetting agent for contact lenses in U.S. Pat. Nos. 3,882,036 and 3,954,644. This nonionic surfactant is a poly(oxyethylene)-poly(oxypropylene) block polymer in admixture with preservatives, viscosity agents and tonicity agents. This particular polymer is said also to have cleaning properties because of its surfactant activity.
The poly(oxyethylene)-poly(oxypropylene) substituted ethylenediamine surfactants used as wetting agents herein also are surface-active agents and thus may be used for the cleansing of contact lenses. A number of non-ionic detergents which can be employed to clean contact lenses are disclosed in U.S. Pat. Nos. 3,882,036 and 3,954,644.
None of the above listed references disclose the use of poly(oxyethylene)-poly(oxypropylene) substituted ethylenediamine surfactants as wetting agents for contact lenses or as cleaning agents for the same.